function re_tr
global p Cinf tr y t
jj=find(p>=0);
if length(jj)>0  
   trdisp2=['系統(tǒng)不穩(wěn)定；系統(tǒng)上升時(shí)間tr無(wú)意義！'];
   helpdlg(trdisp2,'時(shí)域指標(biāo)')
else
   c1=Cinf*0.9;c2=Cinf*0.1;
   mn=find(y>=c2);mh=t(mn(1));
   mn=find(y>=c1);mmh=t(mn(1));
   tr=mmh-mh;                 
   trdisp=['       上升時(shí)間 tr=' num2str(tr) 's'];
   helpdlg(trdisp,'時(shí)域指標(biāo)');
end